Abstract
Starting from a full vehicle model with concentrated masses, excited by inertial and external forces and by road unevenness, the paper realizes equivalent quarter car models “EQC” having the sprung masses excited with corresponding vertical forces and the wheels excited by road This offers a fast evaluation method in pre-dimensioning stage, e.g. the vertical and horizontal stability, the body ground clearance and the comfort. The full vehicle model has four independent suspensions each of them having two degrees of freedom one of the sprung mass and other one for unsprung mass, the wheel being reproduced by stiffness and damping coefficient and the suspension by spring stiffness and shock absorber damping characteristic. The vehicle sprung mass is distributed geometrically to each suspension attach point to the bodywork. Against each sprung masses acts vertical forces generated by the inertial twister of forces and moments acting in the gravity center and by the aerial twister of forces and moments acting in the pressure center. Excepting one situation, the inertial moment generated by distributed masses is different by the real ones, to correct this, the paper proposes to modify the excited moments thus to generate the same vertical accelerations. After validation by comparative simulations on full/ half and quarter car models, the provided quarter car models can offer fast information regarding the suspension performances, the influence of the vehicle geometrical and masses characteristics, the influence of the road longitudinal profile and driver attitude and regarding the effect of the external forces.